It could be that Gillman passing concepts radically reduced interceptions (timing routes, etc...) and Walsh concepts radically increased completion % (horizontal game), both of these factors happen to cause a rise in passer rating (Walsh concepts are built off of Gillman concepts).Passer rating does not measure the quality of the passer, it measures the effectiveness of his average pass. The passing game has become more effective over time as these schematic concepts have filtered through the league. It took to the 90's until Gillman concepts reached league-wide saturation, and to the 00's until Walsh concepts reached league wide saturation.And this fact is readily visible given that the lineage of Walsh QB's, prior to widespread dissemination of his concepts, utterly dominate the NFL in the rating statistic from the point where he is elevated to offensive designer in the late 60's.Yet some are so convinced that rules are the culprit for the change in stats. The passing game has become more and more effective over time because of advances in passing, not because rules are making it easier. It should be no surprise that a statistic meant to measure pass effectiveness is rising over time given that advances in passing are making passing attacks more effective.The QB explosion of the 80's (Marino does not own the record for passing yards per game, that honor goes to Fouts in the strike shortened 1982) has a lot to do with passing rule changes. For bulk stats it also happens that the LBE rule changes correspond with an extra 2 games a year. But it also has a lot to do with the fact that NFL defenses in the 1980's had some serious structural flaws that were easily exploited by creative offensive coordinators.There has been this pervasive run to win concept in the NFL among coaches and talking heads forever. A lot of coaches are overly conservative by nature. Passing has been the most effective way to move the ball going back to the 1940's. In the 70's this whole run first philosophy really took over the NFL. The run pass ratio flipped in the 80's but had been trending that way since the 40's. However the flip almost occurred in the late 60's, for some reason there was a strong regression to the run in the 70's.Born in the 70's (at the pro level) were the over/undershifted 4-3, the fairbanks bullogh 3-4, and the 46. All 3 were designed primarily to stop the run. By the 80's the F-B 3-4 rose as the dominant defense in the NFL. Defenses didn't really use sub-packages much at all. When Fouts came out 4 wide with his Super Chargers offense he was able to slice through run defenses of the day like they weren't even there. Same thing with Marino and his passing attack and Montana and his.Defenses in the early-mid 80's had no answer for teams that based their offense on non-play action passing. Defenses were designed to stop the run and the play action pass that comes with it. Too many analysts (and coaches) are still stuck in this stupid rut that the 70's created where the whole of their understanding revolves around the run and the play action pass. At first DC's had no answer for teams who based their offensive attack around the pass, pass to run teams. They adapted over time.While the rule changes certainly played a big role in the passing explositon of the 80's, just as much to blame is the strange tactics of the 70's and how ######ed it made some coaches, and how easily some creative coaches (and their QB's) were able to slice through the things they were doing.
